Modeling of weak acid production by the EDB method

The electrodialysis with bipolar membrane (EDB) of organic acid salts is an alternative way of the production of organic acids. In this work a model of the basic EDB cell consisting of three compartments (acid, salt, base) is presented. The transport of ions through monopolar ion-exchange membranes is described by the extended Nernst-Planck equation, assuming the Donnan equilibrium at the boundary solution I membrane. The diffusion of undissociated acid and the electro-osmotic flow of water is taken into account. The model predicts how the efficiency of salt conversion, the resistance of cell, the volumes of acid, salt, and base solutions change with time for a given current density. The simulation results are presented for the acetic acid. The influence of nonideality of membranes and of the acid dissociation constant on the efficiency of acid production is shown. (C) 2006 Elsevier B.V. All rights reserved.